Slurry HDC provides a method for the conversion of high boiling, low value petroleum fractions into higher value liquid products. Slurry HDC technology can process difficult feeds, such as feeds with high Conradson carbon residue (CCR), while still maintaining high liquid yields. In addition to resid feeds, slurry HDC units have been used to process other challenging streams present in refinery/petrochemical complexes such as deasphalted rock, steam cracked tar, and visbreaker tar.
Slurry HDC can be performed by processing a feed in one or more slurry HDC reactors. The reaction conditions in a slurry HDC reactor can vary based on the nature of the catalyst, the nature of the feed, the desired products, and/or the desired amount of conversion. The processing conditions in a slurry HDC reactor can be selected to achieve a desired level of conversion of a heavy oil feedstock, such as at least about 80% conversion of the feedstock to products boiling below 975° F. (or another conversion temperature), or at least about 85% conversion, or at least about 90% conversion, or at least about 95% conversion, or at least about 97.5% conversion. The remaining unconverted portion of the feed from slurry HDC represents an unconverted bottoms or “pitch” product.
The pitch generated during slurry HDC is often a challenging product to handle within a refinery. The pitch from a slurry HDC reactor tends to have both a high metals content and a high CCR weight percentage.
Pitch disposition from slurry HDC technologies (e.g. VCC®, Uniflex®, and Microcat) is problematic. Pitch disposition in a liquid form has storage, shipping, and stability issues. The liquid pitch cannot be fluxed economically with a reasonable amount of flux such that it can be sold and/or used as fuel oil. Furthermore, the liquid pitch may contain solids preventing fluxing, which may prevent the liquid pitch from meeting the solids specifications for fuel oils. As such, both producer and purchaser of the pitch are likely to require dedicated facilities to handle the liquid pitch.
Commonly assigned co-pending U.S. Provisional Patent Application No. 61/837,330, filed on Jun. 20, 2013, entitled “Slurry Hydroconversion and Coking of Heavy Oils” discloses various options for disposing of slurry HDC pitch, the disclosure of which is hereby incorporated herein by its entirety. The slurry HDC pitch can be used as a filler material for another application (e.g., the pitch can potentially be used as additional material for asphalt production). Another option for handling the slurry HDC pitch is to attempt to coke the pitch from a slurry HDC. Using the pitch as a portion of a feed to a coker can pose a variety of challenges. An option for processing the pitch that avoids a possible intermediate upgrading step is to use the pitch as at least a portion of a feed to a partial oxidation (POX) process.
The pitch can be used as a fuel in a cement production plant and other production facilities. However, due to the high metals content, the pitch may require further processing in order to be suitable for use even in this application. Additionally, in order to send the material off-site may require the pitch to undergo an additional treatment to solidify or pelletize to make the molecules more transportable. The pelletized HDC pitch could be sold as a free flowing solid having a greater heating power than conventional petcoke or coal.
The pelletization of HDC pitch requires a certain softening point (as measured, for example, by ASTM D36 (Ring and Ball) or ASTM D3461 (Cup and Ball)) to prevent agglomeration when pellets are subjected to load stresses during transport to the end user. Achieving a desired or target softening point can be accomplished in part by having relatively deep cuts and a high initial boiling points of the pitch. However, in order to accomplish this for certain feedstocks, especially those used in connection slurry HDC processing, the reaction conditions in slurry HDC process may need to be altered, which may adversely impact the slate of products produced from the slurry HDC process. There is a need to adjust the softening point of pellets produced from slurry HDC pitch without altering the slurry HDC process or the product slate resulting therefrom.